Biomedical subjects

Hermann Zeumer

Publications and source records attributed to Hermann Zeumer.

23 records · Page 2Linked to original sources

PubMed2003

Sensitivity and interrater agreement of CT and diffusion-weighted MR imaging in hyperacute stroke.

BACKGROUND AND PURPOSE: Previous acute stroke studies found diffusion-weighted (DW) imaging superior to CT for detection of early ischemic signs (EIS). However, these findings were confounded by a large time interval in favor of DW imaging. We compared DW images and CT scans obtained with a short time delay in patients with acute stroke to define the sensitivity and interrater agreement of both imaging techniques. METHODS: CT scans and DW images were obtained within 6 hours of symptom onset in 46 patients with acute stroke. Three neuroradiologists and three neurologists reviewed the images for EIS in five regions of the middle cerebral artery (MCA) territory and estimated the extent of EIS (< or > one-third of the MCA territory). RESULTS: The mean delay between imaging with both modalities was 24.5 minutes (range, 10-41 minutes). Forty-five of 46 patients had an ischemic stroke. EIS were seen on 33 of 45 CT scans (73% sensitivity; 95% confidence interval [CI]: 58-85%) and on 42 of 45 DW images (93% sensitivity; 94% CI: 82-99%). Interrater agreement was moderate (kappa = 0.57) for CT and excellent (kappa = 0.85) for DW imaging. CT studies had a moderate interrater agreement for estimation of EIS greater than one-third of the MCA territory (kappa = 0.40), whereas DW imaging showed good results (kappa = 0.68). Sensitivity for detection of greater than one-third of the MCA territory was equally poor (57%, 95% CI: 29-82%) for both CT and DW imaging. CONCLUSION: DW imaging helped identify EIS with higher sensitivity than that of CT. The interrater variability of the one-third rule was high for CT, and thus the clinical applicability of CT is limited. Our results support the application of stroke MR imaging for the treatment of patients with acute stroke.

Acute Disease↗

PubMed2002

Endovascular therapy of acute vertebrobasilar occlusion: early treatment onset as the most important factor.

In view of the poor prognosis for patients with acute intracranial vertebrobasilar occlusion (VBO), factors were sought that predict survival and good neurologic outcome after acute endovascular treatment by means of local intra-arterial fibrinolysis (LIF) and percutaneous transluminal angioplasty (PTA). LIF was performed in 83 patients with angiographically established acute VBO. A significant residual stenosis after LIF was treated by additional PTA in 8 patients. The types of occlusion were classified as either embolic occlusion (EO) or atherothrombotic occlusion (AO). Outcome was evaluated after 3 months by the Barthel Index (BI) as favorable (BI >90), unfavorable (BI <90) or death and compared for each of 3 diagnostic or treatment variables: recanalization success, occlusion type and time to treatment. Four fibrinolytic treatment modes [urokinase, low-dose and high-dose recombinant tissue-type plasminogen activator (rt-PA), rt-PA + Lys-plasminogen] were also analyzed. The outcome was favorable in 19 patients (23%), unfavorable in 14 (17%) and 50 died (60%). Recanalization was successful in 54 patients (66%). The neurologic outcome was better in recanalized than in nonrecanalized patients (favorable outcome: 30 vs. 10%, mortality: 54 vs. 72%; p = 0.118). The neurologic outcome was better in EO than in AO (favorable outcome: 31 vs. 17%, mortality: 47 vs. 70%, p = 0.112). Under combined treatment by LIF and PTA in 8 patients with AO, 4 survived, 3 with a favorable outcome (38%). Early treatment onset ( 6 h; favorable outcome: 36 vs. 7%, mortality: 52 vs. 70%, p = 0.005). Although no statistically significant differences were found between the types of fibrinolytic agents, treatment with rt-PA and Lys-plasminogen tended toward better results. Early treatment onset proved to be the most important factor for successful endovascular therapy in acute VBO, whereas recanalization and presence of an embolic occlusion also tended toward better results. Additional PTA may be a promising therapy in cases of significant residual stenosis after LIF.

Acute Disease↗

PubMed2002

Correlation of apparent diffusion coefficient and computed tomography density in acute ischemic stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging is very sensitive for the detection of restricted molecular water diffusion in acute ischemic stroke. CT is sensitive to net water uptake in ischemic edema. We compared the decrease in the apparent diffusion coefficient (ADC) in diffusion-weighted MR imaging with CT density changes to study the correlation between diffusion restriction and water uptake in acute stroke patients. METHODS: Twenty-five patients with acute ischemic stroke of the anterior cerebral circulation underwent MR and CT imaging 1.3 to 5.4 hours after symptom onset. ADC and CT data were transferred into a common 3-dimensional space, and regions of decreased ADC (dADC) were superimposed onto the corresponding CT. Mean values of ADC and Hounsfield units (HU) were determined in comparison with the nonaffected hemisphere. RESULTS: Mean decrease in ADC (dADC) was 170+/-53x 10(-6) mm2/s and corresponded to a decrease (dCT) in CT density of 1.3+/-0.7 HU. dCT showed a continuous linear decrease of 0.4 HU/h (r=0.55, P<0.01), whereas the decrease is ADC was almost complete after 1.5 hours. A correlation between the decrease in ADC and dCT was found (r=0.41, P=0.04). CONCLUSIONS: The severity of diffusion restriction correlates with net water uptake in acute ischemic stroke. However, the underlying pathophysiology and different time courses indicate a common reason rather than a direct causality for both phenomena. The time delay and low value of CT density changes provide a reasonable explanation for the higher sensitivity of MR imaging in ischemic stroke.

Acute Disease↗

PubMed2002

Cerebral blood flow predicts lesion growth in acute stroke patients.

BACKGROUND AND PURPOSE: We sought to study the role of MRI-derived cerebral blood flow (CBF) measurements for the prediction of lesion development in acute stroke patients. METHODS: Thirty-two patients were treated with tissue plasminogen activator. Diffusion-weighted (DWI) and perfusion-weighted MRI, T2-weighted imaging, and MR angiography were performed before treatment (2.8+/-0.9 hours after symptom onset) and on follow-up (days 1 and 7). CBF thresholds (12 and 22 mL/100 g per minute) were applied to bolus tracking MRI maps to determine predictive cutoff levels. RESULTS: In 21 patients (group A), the terminal lesion volume (T2-weighted imaging) was larger than the initial DWI lesion volume (89+/-93 versus 21+/-38 mL). In 11 patients (group B), the terminal lesion volume was smaller than the initial DWI lesion volume (7+/-27 versus 15+/-29 mL). The initial DWI lesion volume did not differ between both groups. The presence of a tissue volume > or =50 mL with a CBF value < or =12 mL/100 g per minute was predictive for lesion enlargement to day 7 in T2-weighted imaging (positive predictive value, 0.80). CONCLUSIONS: The presence of a tissue volume > or =50 mL with a CBF value < or =12 mL/100 g per minute predicts further lesion growth in hyperacute stroke patients. MRI-derived CBF values, with all their present limitations, are valuable in early estimation of prognosis of stroke patients.

Acute Disease↗

PubMed2002

Severe ADC decreases do not predict irreversible tissue damage in humans.

BACKGROUND AND PURPOSE: A mismatch between diffusion- and perfusion-weighted MRI is thought to define tissue at risk of infarction. This concept is based on the assumption that diffusion slowing of and decreases in the apparent diffusion coefficient (ADC) serve as indicator of tissue proceeding to infarction. We tested this hypothesis. METHODS: MRI (diffusion weighted, perfusion weighted, MRA, T2 weighted) was performed in 15 patients with acute stroke within 2.9+/-0.8 hours (mean+/-SD) of onset and on days 1 and 7. After intraindividual realignment of the ADC maps, the development of ADC range volumes and ADC values was determined. RESULTS: An increase (354%, group A1) in the total ADC-based lesion volume below a threshold of < 80% occurred in 4 patients on day 1, persisting on day 7 with a pronounced increase of ADC range volumes with low ADC values. An increase in total ADC-based lesion volume (201%, group A2) followed by a secondary drop to day 7 was found in 7 patients. A significant reduction in total ADC-based lesion volume (14%, group B) was found in 4 patients. ADC-based lesion volume increase was associated with persistent vessel occlusion in group A, whereas recanalization in group B resulted in ADC volume decrease. ADC normalization was observed independently from the degree of the initial ADC decrease on days 1 and 7 in group B. CONCLUSIONS: In line with results from animal experiments, ADC decreases do not reliably indicate tissue infarction Even severely decreased ADC values may normalize in human stroke, and it seems likely that ADC normalization depends on the duration and severity of ischemia rather than the absolute value.

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